Erythrocytic metabolism of ATLX-0199: An agent that increases minute ventilation.

Both L- and D-isomers of S-nitrosocysteine (CSNO) can bind to the intracellular domain of voltage-gated potassium channels in vitro. CSNO binding inhibits these channels in the carotid body, leading to increased minute ventilation in vivo. However, only the l-isomer is active in vivo because it requires the l-amino acid transporter (LAT) for transmembrane transport. In rodents and dogs, the esterified D-CSNO precursor-d-cystine dimethyl ester (ATLX-0199)-overcomes opioid- and benzodiazepine-induced respiratory depression while maintaining analgesia. Although ATLX-0199 can enter cells independently of LAT because it is an ester, its stability in plasma is limited by the presence of esterases. Here, we hypothesized that the drug could be sequestered in erythrocytes to avoid de-esterification in circulation. We developed a liquid chromatography-mass spectrometry method for detecting ATLX-0199 and characterized a new metabolite, S-nitroso-d-cysteine monomethyl ester (DNOCE), which is also a D-CSNO precursor. We found that both ATLX-0199 and DNOCE readily enter erythrocytes and neurons and remain stable over 20 min; thus ATLX-0199 can enter cells where the ester is stable, but the thiol is reduced. Depending on hemoglobin conformation, the reduced ester can be S-nitrosylated and enter carotid body neurons, where it then increases minute ventilation. These data may help explain the paradox that ATLX-0199, a dimethyl ester, can avoid de-esterification in plasma and exert its effects at the level of the carotid body.

Pediatric pulmonology year in review 2020: Physiology.

Pulmonary physiology is a core element of pediatric pulmonology care and research. This article reviews some of the notable publications in physiology that were published in Pediatric Pulmonology in 2020.

Effectiveness and preclinical safety profile of doxycycline to be used "off-label" to induce therapeutic transgene expression in a phase I clinical trial for glioma.

Glioblastoma multiforme (GBM) is the most common malignant primary brain cancer in adults; it carries a dismal prognosis despite improvements in standard of care. We developed a combined gene therapy strategy using (1) herpes simplex type 1-thymidine kinase in conjunction with the cytotoxic prodrug ganciclovir to kill actively proliferating tumor cells and (2) doxycycline (DOX)-inducible Fms-like tyrosine kinase 3 ligand (Flt3L), an immune stimulatory molecule that induces anti-GBM immunity. As a prelude to a phase I clinical trial, we examined the efficacy and safety of this approach (Muhammad et al., 2010, 2012). In the present article, we investigated the efficacy and safety of the "off-label" use of the antibiotic DOX to turn on the high-capacity adenoviral vector (HC-Ad) encoding therapeutic Flt3L expression. DOX-inducible Flt3L expression in male Lewis rats was assessed using DOX doses of 30.8 mg/kg/day (low-DOX) or 46.2 mg/kg/day (high-DOX), which are allometrically equivalent (Voisin et al., 1990) to the human doses that are recommended for the treatment of infections: 200 or 300 mg/day. Naïve rats were intracranially injected with 1×10(9) viral particles of HC-Ad-TetOn-Flt3L, and expression of the therapeutic transgene, that is, Flt3L, was assessed using immunohistochemistry in brain sections after 2 weeks of DOX administration via oral gavage. The results show robust expression of Flt3L in the rat brain parenchyma in areas near the injection site in both the low-DOX and the high-DOX groups, suggesting that Flt3L will be expressed in human glioma patients at a DOX dose of 200 or 300 mg/day. These doses have been approved by the U.S. Food and Drug Administration to treat infections in humans and would thus be considered safe for an off-label use to treat GBM patients undergoing HC-Ad-mediated gene therapy in a phase I clinical trial.

Synthesis and chemistry of bis(triisopropylphosphine) nickel(I) and nickel(0) precursors.

High yield syntheses of ((i)Pr(3)P)(2)NiX (3a-c), (where X = Cl, Br, I) were established by comproportionation of ((i)Pr(3)P)(2)NiX(2) (1a-c) with ((i)Pr(3)P)(2)Ni(η(2)-C(2)H(4)) (2). Reaction of 1a with either NaH or LiHBEt(3) provided ((i)Pr(3)P)(2)NiHCl (4), along with 3a as a side-product. Reduction of ((i)Pr(3)P)(2)NiCl (3a-c) with Mg in presence of nitrogen saturated THF solutions provided the dinitrogen complex [((i)Pr(3)P)(2)Ni](2)(µ-η(1):η(1)-N(2)) (5). In aromatic solvents such as benzene and toluene a thermal equilibrium exists between 5 and the previously reported monophosphine solvent adducts ((i)Pr(3)P)Ni(η(6)-arene) (6a,b). Reaction of 5 with carbon dioxide provided ((i)Pr(3)P)(2)Ni(η(2)-CO(2)) (7). Thermolysis of 9 at 60 °C provided a mixture of products that included the reduction product ((i)Pr(3)P)(2)Ni(CO)(2) (8) along with (i)Pr(3)P=O, as identified by NMR spectroscopy. Complex 8 was also prepared in high yield from the reaction of 5 with CO. Reaction of 5 with CS(2) gave the dimeric carbon disulfide complex [((i)Pr(3)P)Ni(µ-η(1):η(2)-CS(2))](2) (9). Diphenylphosphine reacts with 5 to form the dinuclear Ni(I) complex [((i)Pr(3)P)Ni(µ(2)-PPh(2))](2) (10). Complex 5 reacts with PhSH to form ((i)Pr(3)P)(2)Ni(SPh)(H) (11), which slowly loses H(2) and (i)Pr(3)P to form the dimeric Ni(I) complex [((i)Pr(3)P)Ni(µ(2)-SPh)](2) (12) at room temperature. Complex 12 was also accessed by salt metathesis from the reaction of ((i)Pr(3)P)(2)NiCl (3a) with PhSLi, which demonstrates the utility of 3a as a Ni(I) precursor. With the exception of 6a,b, all compounds were structurally characterized by single-crystal X-ray crystallography.